help - very hard

Advanced methods and approaches for solving Sudoku puzzles

help - very hard

Postby BadCujo » Mon Jun 27, 2005 4:53 pm

I have the following in a column

{17}{8}{2}{4}{12567}{3567}{367}{9}{367}

Question : does the combination 3567 in cells 5,6,7,9 allow me to remove 1 as a candidate in cell 5?
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Postby scrose » Mon Jun 27, 2005 5:03 pm

No. If you are looking for a quad, the four numbers in the quad must appear only in four cells. However, in your example the candidate 7 appears in five cells.
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Postby BadCujo » Mon Jun 27, 2005 5:13 pm

Thanks. I'll keep looking
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Postby BadCujo » Tue Jun 28, 2005 11:09 am

OK, I must be blind. I am not seeing a way to move forwrd here.

*64 3** 8*9
895 4** 7**
2*3 **9 ***

4*9 2*8 36*
*** *9* *8*
*8* **4 9*1

*** 9** 5*8
958 **7 *4*
**1 **5 *9*
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Postby angusj » Tue Jun 28, 2005 11:16 am

BadCujo wrote:OK, I must be blind. I am not seeing a way to move forwrd here.

Look for what I call naked pairs and naked triples .
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Postby Animator » Tue Jun 28, 2005 11:20 am

First take a really good look at box 2.
Then take a reallly good look at row 3.
Look at box 3, and decided what it means for column 8.
Look at column 8 and fill in a number in column 7.
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Postby BadCujo » Tue Jun 28, 2005 12:12 pm

OK. One step at a time.
In box three I see 3 cells only that can contain a 5,7 or 8

Based on that I can remove the 1's 2's and 6's from those cells?
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Postby BadCujo » Tue Jun 28, 2005 12:13 pm

previous post.... I meant box 2.... sorry
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Postby Animator » Tue Jun 28, 2005 12:18 pm

That is correct.

(Note though that you can come to the same conclusion by looking at the numbers 1, 2 and 6)
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Postby angusj » Tue Jun 28, 2005 12:24 pm

BadCujo wrote:OK. One step at a time.
In box three I see 3 cells only that can contain a 5,7 or 8
Based on that I can remove the 1's 2's and 6's from those cells?

Yes, that's right - you've got it. Also, note that the 1s, 2s and 6s form a 'naked triple' in that box - I often find them easier to spot than the 'hidden triple' you found.
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Postby BadCujo » Tue Jun 28, 2005 12:56 pm

Ahhhhh! I see that now. When I cover my right eye I see the 126.... I had my left eye covered at the time ;-)

I now see the pair 46 in box 3 to eliminate the 1 in c7 & 5 in c9 and also the 6 in r2c9 (i was using both eyes)
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